The present invention is directed to sheets suitable as receiving substrates in electrostatic printing and imaging processes. More specifically, the present invention is directed to coated recording sheets suitable for electrostatic printing and imaging processes which contain one or more antistatic layers and one or more toner receiving layers. One embodiment of the present invention is directed to a recording sheet which comprises a base sheet, an antistatic layer coated on at least one surface of the base sheet comprising a mixture of a first component selected from the group consisting of hydrophilic polysaccharides and a second component selected from the group consisting of poly (vinyl amines), poly (vinyl phosphates), poly (vinyl alcohols), poly (vinyl alcohol)-ethoxylated, poly (ethylene imine)-ethoxylated, poly (ethylene oxides), poly (n-vinyl acetamide-vinyl sulfonate salts), melamine-formaldehyde resins, urea-formaldehyde resins, styrene-vinylpyrrolidone copolymers, and mixtures thereof, and at least one toner receiving layer coated on an antistatic layer comprising a material selected from the group consisting of maleic anhydride containing polymers, maleic ester containing polymers, and mixtures thereof.
Electrostatic imaging processes are known. For example, the formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrophotographic imaging process, as taught by C. F. Carlson in U.S. Pat. No. 2,297,691, entails placing a uniform electrostatic charge on a photoconductive insulating layer known as a photoconductor or photoreceptor, exposing the photoreceptor to a light and shadow image to dissipate the charge on the areas of the photoreceptor exposed to the light, and developing the resulting electrostatic latent image by depositing on the image a finely divided electroscopic material known as toner. The toner will normally be attracted to those areas of the photoreceptor which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This developed image may then be transferred to a substrate such as paper. The transferred image may subsequently be permanently affixed to the substrate by heat, pressure, a combination of heat and pressure, or other suitable fixing means such as solvent or overcoating treatment.
Other methods for forming electrostatic latent images are also known, such as ionographic methods. In ionographic imaging processes, a latent image is formed on a dielectric image receptor or electroreceptor by ion deposition, as described, for example, in U.S. Pat. Nos. 3,564,556, 3,611,419, 4,240,084, 4,569,584, 2,919,171, 4,524,371, 4,619,515, 4,463,363, 4,254,424, 4,538,163, 4,409,604, 4,408,214, 4,365,549, 4,267,556, 4,160,257, and 4,155,093, the disclosures of each of which are totally incorporated herein by reference. Generally, the process entails application of charge in an image pattern with an ionographic writing head to a dielectric receiver that retains the charged image. The image is subsequently developed with a developer capable of developing charge images.
Many methods are known for applying the electroscopic particles to the electrostatic latent image to be developed. One development method, disclosed in U.S. Pat. No. 2,618,552, is known as cascade development. Another technique for developing electrostatic images is the magnetic brush process, disclosed in U.S. Pat. No. 2,874,063. This method entails the carrying of a developer material containing toner and magnetic carrier particles by a magnet. The magnetic field of the magnet causes alignment of the magnetic carriers in a brushlike configuration, and this "magnetic brush" is brought into contact with the electrostatic image bearing surface of the photoreceptor. The toner particles are drawn from the brush to the electrostatic image by electrostatic attraction to the undischarged areas of the photoreceptor, and development of the image results. Other techniques, such as touchdown development, powder cloud development, and jumping development are known to be suitable for developing electrostatic latent images.
Recording sheets suitable for various printing and imaging processes are also known. For example, U.S. Pat. No. 4,997,697 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparent substrate material for receiving or containing an image which comprises a supporting substrate base, an antistatic polymer layer coated on one or both sides of the substrate comprising hydrophilic cellulosic components, and a toner receiving polymer layer contained on one or both sides of the antistatic layer comprising hydrophobic cellulose ethers, hydrophobic cellulose esters, or mixtures thereof, and wherein the toner receiving layer contains adhesive components.
In addition, U.S. Pat. No. 4,370,379 (Kato et al.) discloses a transfer film comprising a transparent plastic film substrate, an undercoating layer composed of an electrically conductive resin and having a surface resistance of 1.0.times.10.sup.6 to 9.0.times.10.sup.9 ohms, and a toner receiving layer composed of a binder resin and having a surface resistance of 1.0.times.10.sup.10 to 1.0.times.10.sup.14 ohms, which is formed on at least one surface of the transparent plastic film substrate through the undercoating layer.
Further, U.S. Pat. No. 4,480,003 (Edwards et al.) discloses a transparency film for use in a plain paper electrostatic copier. The transparency film comprises (a) a flexible, transparent, heat resistant, polymeric film base, (b) an image receiving layer carried upon a first major surface of the film base, and (c) a layer of electrically conductive material carried on a second major surface of the film base. Where necessary, a primer coat is interposed between the image receiving layer and the film base and/or between the layer of electrically conductive material and the film base. A protective coating is preferably applied over the layer of conductive material. The film can be used in powder-toned or liquid-toned plain paper copiers for making transparencies.
Additionally, U.S. Pat. No. 4,711,816 (Wittnebel) discloses a transparency sheet material for use in a plain paper electrostatic copier comprising (a) a flexible, transparent, heat resistant, polymeric film base, (b) an image receiving layer carried upon a first major surface of the film base, and (c) a layer of electrically conductive prime coat interposed between the image receiving layer and the film base. The sheet material can be used in powder-toned or liquid-toned plain paper copiers for making transparencies.
U.S. Pat. No. 4,865,914 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparency which comprises a supporting substrate and a blend which comprises polyethylene oxide and carboxymethyl cellulose together with a component selected from the group consisting of (1) hydroxypropyl cellulose; (2) vinylmethyl ether/maleic acid copolymer; (3) carboxymethyl hydroxyethyl cellulose; (4) hydroxyethyl cellulose; (5) acrylamide/acrylic acid copolymer; (6) cellulose sulfate; (7) poly(2-acrylamido-2-methyl propane sulfonic acid); (8) poly(vinyl alcohol); (9) poly(vinyl pyrrolidone); and (10) hydroxypropyl methyl cellulose. Papers with these coatings are also disclosed.
U.S. Pat. No. 5,006,407 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparency which comprises a hydrophilic coating and a plasticizer such as a phosphate, a substituted phthalic anhydride, a glycerol, a glycol, a substituted glycerol, a pyrrolidinone, an alkylene carbonate, a sulfolane, or a stearic acid derivative. Papers having the disclosed coatings are also included in the disclosure.
U.S. Pat. No. 4,956,225 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses transparencies suitable for electrographic and xerographic imaging which comprise a polymeric substrate with a toner receptive coating on one surface comprising blends of: poly(ethylene oxide) and carboxymethyl cellulose; poly(ethylene oxide), carboxymethyl cellulose and hydroxypropyl cellulose; poly(ethylene oxide) and vinylidene fluoride/hexafluoropropylene copolymer, poly(chloroprene) and poly(.alpha.-methylstyrene); poly(caprolactone) and poly(.alpha.-methylstyrene); poly(vinylisobutylether) and poly(.alpha.-methylstyrene); blends of poly(caprolactone) and poly(p-isopropyl .alpha.-methylstyrene); blends of poly(1,4-butylene adipate) and poly(.alpha.-methylstyrene); chlorinated poly(propylene) and poly(.alpha.-methylstyrene); chlorinated poly(ethylene) and poly(.alpha.-methylstyrene); and chlorinated rubber and poly(.alpha.-methylstyrene). This copending application also discloses transparencies suitable for electrographic and xerographic imaging processes comprising a supporting polymeric substrate with a toner receptive coating on one surface thereof which comprises: (a) a first layer coating of a crystalline polymer selected from the group consisting of poly(chloroprene), chlorinated rubbers, blends of poly(ethylene oxide), and vinylidene fluoride/hexafluoropropylene copolymers, chlorinated poly(propylene), chlorinated poly(ethylene), poly(vinylmethyl ketone), poly(caprolactone), poly(1,4-butylene adipate), poly(vinylmethyl ether), and poly(vinyl isobutylether); and (b) a second overcoating layer comprising a cellulose ether selected from the group consisting of hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and ethyl cellulose.
U.S. Pat. No. 5,068,140 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses a transparent substrate material for receiving or containing an image which comprises a supporting substrate, an anticurl coating layer or coatings thereunder, and an ink receiving layer thereover.
U.S. Pat. No. 5,139,903 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses an imaged transparency comprising a supporting substrate, an oil absorbing layer which comprises, for example, chlorinated rubber, styrene-olefin copolymers, alkylmethacrylate copolymers, ethylenepropylene copolymers, sodium carboxymethyl cellulose or sodium carboxymethylhydroxyethyl cellulose, and ink receiving polymer layers comprising, for example, vinyl alcohol-vinyl acetate, vinyl alcohol-vinyl butyral or vinyl alcohol-vinyl acetate-vinyl chloride copolymers. The ink receiving layers may include therein or thereon fillers such as silica, calcium carbonate, or titanium dioxide.
U.S. Pat. No. 5,075,153 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a never-tear coated paper comprising a plastic supporting substrate; a binder layer comprising polymers selected from the group consisting of (1) hydroxy propyl cellulose, (2) poly(vinyl alkyl ether), (3) vinyl pyrrolidone-vinyl acetate copolymer, (4) vinyl pyrrolidonedialkylamino ethyl methacrylate copolymer quaternized, (5) poly(vinyl pyrrolidone), (6) poly(ethylene imine), and mixtures thereof; a pigment or pigments; and an ink receiving polymer layer.
U.S. Pat. No. 5,137,773 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses all purpose xerographic transparencies with coatings thereover which are compatible with the toner compositions selected for development, and wherein the coatings enable images with acceptable optical densities. One disclosed transparency for ink jet printing processes and xerographic printing processes comprises a supporting substrate and a coating composition thereon which comprises a mixture selected from the classes of materials comprising (a) nonionic celluloses such as hydroxylpropylmethyl cellulose, hydroxyethyl cellulose, hydroxybutyl methyl cellulose, or mixtures thereof; (b) ionic celluloses such as anionic sodium carboxymethyl cellulose, anionic sodium carboxymethyl hydroxyethyl cellulose, cationic celluloses, or mixtures thereof; (c) poly(alkylene oxide) such as poly(ethylene oxide) together with a noncellulosic component selected from the group consisting of (1) poly(imidazoline) quaternized; (2) poly(N,N-dimethyl-3,5-dimethylene piperidinium chloride); (3) poly(2-acrylamido-2-methyl propane sulfonic acid); (4) poly(ethylene imine) epichlorohydrin; (5) poly(acrylamide); (6) acrylamide-acrylic acid copolymer; (7) poly(vinyl pyrrolidone); (8) poly(vinyl alcohol); (9) vinyl pyrrolidone-diethyl aminomethylmethacrylate copolymer quaternized; (10) vinyl pyrrolidone-vinyl acetate copolymer; and mixtures thereof. The coating compositions are generally present on both sides of a supporting substrate, and in one embodiment the coating comprises nonionic hydroxyethyl cellulose, 25 percent by weight, anionic sodium carboxymethyl cellulose, 25 percent by weight, poly(ethylene oxide), 25 percent by weight, and poly(acrylamide), 25 percent by weight. The coating can also contain colloidal silica particles, a carbonate, such as calcium carbonate, and the like primarily for the purpose of transparency traction during the feeding process.
Copending application U.S. Ser. No. 07/544,577 (Malhotra), filed Jun. 27, 1990, now U.S. Pat. No. 5,202,205 the disclosure of which is totally incorporated herein by reference, discloses transparencies for electrophotographic processes, especially xerographic processes, ink jet printing processes, dot matrix printing processes and the like, comprising a supporting substrate and an ink or toner receiving coating composition on both sides of the substrate comprising an adhesive layer polymer such as chlorinated poly(isoprene), chlorinated poly(propylene), blends of phosphate esters with poly(styrene) and the like and an antistatic layer on both sides of the adhesive layer, which antistatic layer comprises complexes of metal halides such as potassium iodide, urea compounds such as urea phosphate with polymers containing oxyalkylene units such as poly(ethylene oxide), poly(propylene oxide), ethylene oxide/propylene oxide block copolymers, ethoxylated amines and the like, and an optional resin binder polymer such as poly(2-hydroxyethylmethacrylate), poly(2-hydroxypropylmethacrylate), hydroxypropylmethyl cellulose, or the like.
Copending application U.S. Ser. No. 07/561,430 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a recording sheet which comprises, in the order stated, an ink receiving layer, a base sheet, a heat absorbing layer, and an anticurl layer. The recording sheet can be transparent or opaque, and can be used in a wide variety of printing and imaging processes. The recording sheet exhibits little or no curling, even after exposure to heat and/or a wide range of relative humidities.
Although known recording sheets are suitable for their intended purposes, a need remains for recording sheets that enable formation of images of excellent quality with high resolution and little or no background deposits. In addition, there continues to be a need for transparent recording sheets that enable formation of images with high optical density. Further, there is a need for transparent recording sheets suitable for use in electrostatic imaging processes and having a base sheet, one or more antistatic layers, and one or more toner receiving layers, wherein the antistatic layer and toner receiving layer exhibit excellent adhesion to the base sheet. There is also a need for recording sheets suitable for use in electrostatic imaging processes that enable excellent adhesion between the toner image and the recording sheet. Additionally, there is a need for recording sheets suitable for use in electrostatic imaging processes that can be used in more than one type of electrostatic imaging apparatus. Further, there is a need for recording sheets that do not block (stick together) under conditions of high relative humidity (for example, 50 to 80 percent relative humidity) and high temperature (for example, over 50.degree. C.). There is also a need for transparent recording sheets suitable for use in electrostatic imaging processes that enable increased toner flow over the sheet during the imaging process. Additionally, there is a need for transparent recording sheets suitable for use in electrostatic imaging permit the substantial elimination of beading during mixing of primary colors to generate secondary colors. Further, there is a need for transparent recording sheets suitable for use in electrostatic imaging processes that exhibit substantial image permanence for extended time periods.